AIDS Drug Assistance Programs (ADAPs) are federally-funded, state-administered programs that act as the drug "safety net" for primarily low-income, underinsured, or uninsured HIV- infected individuals. ADAPs may differ from state to state based on financial eligibility criteria, cost-containment measures, and inclusiveness of drug formularies with respect to antiviral therapies, opportunistic infection prophylaxis, and addiction treatment. These variations in state ADAP policies may result in similar HIV-infected persons having different health outcomes due to their state of residence. The objective of this research is to determine the association between specific structural features of state ADAPs on individual-level clinical outcomes among HIV-infected persons in the United States between 1998 and 2008. This will be conducted based on data from persons living in 25 states who are part of the North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD). Aim 1 of this research will determine the level of heterogeneity in health outcomes by state of residence with respect to HAART initiation (among those who are eligible for treatment initiation based on clinical guidelines) and one-year HIV virologic response and one- and three-year mortality (among those initiating HAART), controlling for individual-level factors, state-level factors, and calendar time. Aim 2 will examine the association between selected state ADAP structural features on HAART initiation among clinically eligible persons using multilevel modeling strategies, controlling for potential confounders. Finally, Aim 3 will determine the association between selected state ADAP structural features and one-year HIV virologic response and one- and three-year mortality among persons initiating HAART using instrumental variable methods. Subgroup analyses will be performed among current and former drug users, many of whom are ADAP clients and who may especially benefit from ADAP services given their lower access to quality care and greater medical needs as a consequence of co-morbidities such as hepatitis C virus infection and opioid addiction.